init commit

3sem/seminars/l4/02.c

@@ -0,0 +1,76 @@
+#include <sys/stat.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <sys/types.h>
+
+int
+acs(const char *name, int mode)
+{
+    struct stat st;
+
+    if (lstat(name, &st) < 0) {
+        return -1;
+    }
+    uid_t uid = getuid();
+    if (uid == 0) {
+        return 0;
+    }
+
+    uid_t st_mode = st.st_mode;
+    if (st.st_mode == uid) {
+        st_mode >>= 6;
+    } else if (st.st_gid == getgid()) {
+        st_mode >>= 3;
+    }
+    st_mode &= 7;
+
+    // for (int i = 0; i < 3; ++i) {
+    //     if (st_mode ^ mode & 1) {
+    //         return -1;
+    //     }
+    //     st_mode >>= 1;
+    //     mode >>= 1;
+    // }
+
+    if (st_mode & mode == mode) {
+        return 0;
+    }
+
+    return -1;
+}
+
+int
+main(int argc, char *argv[])
+{
+    struct stat st;
+
+    for (int i = 1; i < argc; i++) {
+        if (lstat(argv[i], &st) < 0) {
+            continue;
+        }
+
+        char type;
+        if (S_ISREG(st.st_mode)) {
+            type = '-';
+        } else if (S_ISDIR(st.st_mode)) {
+            type = 'd';
+        } else if (S_ISLNK(st.st_mode)) {
+            type = 'l';
+        } else {
+            type = '?';
+        }
+
+        char m[] = "rwxrwxrwx";
+        for (int j = 0; j < 9; j++) {
+            if (!((st.st_mode >> j) & 1)) {
+                m[8 - j] = '-';
+            }
+        }
+
+        printf("%c%s %lu %hu %lu %ld %s\n", type, m, st.st_nlink, st.st_uid, st.st_size, st.st_ctime, argv[i]);
+    }
+    return 0;
+}